Heat exchanger

ABSTRACT

A versatile heat exchanger capable of being used in a modular arrangement. An impervious member separates fluid flow channels, with metal fins extending therethrough and sealed therein so that there is no leakage therethrough.

Unlted States Patent 1 1 1111 3,912,003 Schrade Oct. 14, 1975 [54] HEAT EXCHANGER 2,646,972 7/1953 Schmid 165/183 2,947,152 8 1960 Bl 165 179 X [76] Inventor: Jean Schrade,Ottenberg Str. 8, 3,407,876 0x968 figl lunch, Swltzerland 3,409,075 11/1968 Long Filed: p 10, 1974 3,491,184 l/197O Rletdl k 165/165 X 21 App]. No; 459,468

Primary Examiner-Char1es J. Myhre Assistant Examiner-Theophil W. Streule, Jr. Forelgn Application Prlorlty Data Attorney, Agent, or FirmRobert H. Bachman Apr. 13, 1973 Switzerland 5290/73 [52] US. Cl. 165/165; 165/179; 165/135; T

165/166 [57] ABSTRAC [51] Int. C1, F28F 3/08 A versatile heat exchanger capable of being used in a [58] Fleld of Search 165/ 164-166, modular arrangement An impervious member sepa 165/179, 183, 181, 135; 6 /3 rates fluid flow channels, with metal fins extending therethrough and sealed therein so that there is no [56] References C'ted leakage therethrough.

UNITED STATES PATENTS 1.692391 11/1928 Stancliffe 165/166 10 Claims, 6 Drawing Figures US. Patent 0611. 14, 1975 Sheet 1 012 3,912,003

US. Pat n t bctj14, 1975 Sheet 2 of2 3,912,003

HEAT EXCHANGER BACKGROUND OF THE INVENTION Presently known heat exchangers are always so constructed that a wall made of metal or of another relatively good heat conductor, such as graphite, effects the separation between the two media between which heat is to be exchanged. That separating wall is to conduct heat from the medium that is at higher temperature to the one at lower temperature. Because of the weight and the price, the separating wall is made as thin as possible. Because of the ease in manufacture, this separating wall is usually the wall of a tube. The media between which heat exchange is to be effected are either water, organic liquids, or gases. In all cases they have substantially lower heat conductivity than metals. For that reason, many ways have been proposed and in part executed to increase the surface of the metallic tube wall.

Heat exchangers of the foregoing type are often heavy in weight, bulky and subject to corrosion failure. It is highly desirable to provide a heat exchanger which overcomes these disadvantages, while obtaining good heat transfer efficiency.

Attempts have been made in the art to overcome these disadvantages, for example, as shown in U.S. Pat. Nos. 3,046,639 and 3,103,971. These patents show an interconnected grid of wires extending across fluid flow channels and through separating members. In order to account for differences in heat transfer characteristics from one compartment so formed to another it is necessary to vary the spacing between compartments, which is inconvenient. Units of this type lack the versatility to be suitable for a wide variety of applications and under a wide variety of different conditions.

Accordingly, it is a principal object of the present invention to provide a simple and convenient heat exchanger which is suitable for use under a variety of conditions.

It is a further object of the present invention to provide such a heat exchanger which is light in weight and which is suitable for use in corrosive environments.

Further objects and advantages of the present invention will appear hereinafter.

SUMMARY OF THE INVENTION The present invention resides in a heat exchanger characterized in that it is constructed from different materials, of which only one needs to have good heat conductivity, for example, from metal and plastic, in such a manner that the poor conductor, e.g., the plastic, forms the separating wall between the heat transfer fluid or medium that is to be cooled and the cooling medium, while the good conductor, e.g., the metal, is made to extend through the said separating wall in the shape of lamellae or strips or the like. One advantage of such an arrangement is the corrosion resistant separation that may be brought about between the fluids circulating within the heat exchanger, since the separating wall may be altogether corrosion resistant, its material having been chosen accordingly without said material having to be a good conductor of heat. In the event of corrosion of the heat conducting, e.g., metal components of the device, a gradual reduction in efficiency occurs at first which may be detected long before serious failure so that leaks which can cause fatal defects of the device may be prevented in time.

According to the proposed construction, the surface of the metal that is in heat exchange relationship with the medium is substantially increased compared to a tube. At the same time, an extension by a factor of approximately 10 of the distance over which heat is conducted is recognized as given by the metallic wall consisting of the lamellae. As is known from the formulae applicable to the computation of heat exchangers, the increase of contact surface has marked advantages, while the increase ofthe wall thickness" has negligible influence upon the efficiency of such apparatus.

In an experiment using a heat exchanger according to FIG. 2, heat transfer of 1800 Kcal/h.m C. was obtained with ethylene glycol at 60C. and cooling water at 10C. In this experiment the two portions of the lamellae on the warm and the hot side were not dimensioned optimally, i.e. they were equal and accordingly not adjusted to the respective heat transfer coefficients.

The heat exchanger of the present invention comprises: a first channel for conveying a first heat transfer fluid; a second channel for conveying a second heat transfer fluid; a solid, impervious member separating said first channel and the first fluid circulating therein from the second channel and the fluid circulating therein; a plurality of heat conductive metal fins or finlike elements extending through said member, with a first portion of said fins extending into a part of said first channel and a second portion of said fins extending into a part of said second channel so that the second fluid circulating in the second channel is in heat exchange relationship with the first fluid circulating in the first channel-due to heat being conducted by said fins, said fins being sealed in said member so that there is no fluid leakage through said member, whereby the first portion of said fins extending into the first channel may transfer substantially more heat than the second portion of said fins extending into the second channel if it is desired to compensate for dissimilar heat transfer characteristics of said fluids.

BRIEF DESCRIPTION OF DRAWINGS The nature of the invention will be better understood from the following description taken in conjunction with the accompanying drawings in which specific embodiments have been shown for purposes of illustration.

In the drawings:

FIG. 1 is a sectional view of a representative heat exchanger of the present invention;

FIG. 2 shows a separating member from FIG. 1 with a plurality of fin elements passing therethrough, on a larger scale;

FIG. 3 shows a separating member, on an enlarged scale, with fin elements passing therethrough, from which the separating member of FIG. 2 may be constructed; and

FIGS. 4-6 show variations in the separating member and fin elements.

DETAILED DESCRIPTION In FIG. 1, cover sheets 5 and 6 encase the heat exchanger according to the present invention. Between said cover sheets are the sets of elements 7, 8, 9, 10 which subdivide the space into channels 11, 12, l3, l4 and 15. Elements 7, 8, 9 and 10 embody solid, impervious bulkheads separating the channels, and are preferably constructed of plastic material. Channels 11, 12,

I3, 14 and 15 formed thereby are fluid flow channels for conveying fluids in heat exchange relationship. Thus, a first fluid may be conveyed in channel 11, a second fluid in channel 12, a first fluid in channel 13, a second fluid in channel 14 and a first fluid in channel 15, with the fluids preferably flowing in countercurrent relationship with the fluid flow shown by the arrows. Naturally, the fluid channels are connected to appropriate headers and means to cause the fluids to flow in the channels, as a pump, not shown, all of which are conventional. One of the sets of elements 7, 8, 9, 10 is shown in FIG. 2 on an enlarged scale. Bulkhead 16 consists of a material that need not be a good conductor and may be a corrosion-resistant material, preferably plastic, and lamellae -17 are made of a material that is a good conductor of heat, preferably metal. The lamallae may be made of a single metal or of an alloy and they may have an improved surface or a coated surface or.a clad surface. According to FIG. 2, the two portions of the lamellae that extend out of bulkhead 16 are of equal size'. This need not be so in all instances. For example, if gas circulates on one side and a liquid on the other, then the portions of the lamellae on the gas side may be substantially larger, but also thinner than the portions extending into the liquid. Instead of the shape given in FIGS. 2 and 3, which show the lamellae being flat and rectangular in cross-section, the same lamellae may exhibit a shape which deviates from a geometric plane and the cross-section may be square, round, corrugated, etc. The portion of the lamellae and the bulkhead 16 are bonded together by known methods with a bond that is strong and impervious to liquids.

FIG. 3 shows one specific embodiment of the construction of elements. The bulkhead forming parts 18 and 19 are shown as being identical. As here shown they contain therein clearance holes corresponding to half of the thickness of the corresponding portion of lamellae 20 and 21 etc. The bulkhead components and lamellae may be previously produced, e.g., by pressure molding and stamping, respectively, and assembled into elements of the desired height whereby such assembly may be effected largely automatically. Other embodiments particularly well suited for this type of heat exchanger are based upon the fact the two portions of each lamella extending from bulkhead 16 do not exhibit the same surface on both sides. For example, if the two liquids circulating in channels 12 and 13 have different heat transfer coefficients, such as 2000 for the liquid in channel 12 and 8000 for the one in channel 13, then the portions of the lamella extending from bulkheads 8 and 9 into channel 13 may preferably have a surface which is four times smaller than the surface of the portions extending into channel 12, since each surface unit in channel 13 transfers four times as much heat into the metal of the lamella than the one in channel 12. Thereby, the overall volume is reduced and the heat exchanger reduced in size without loss of heat transfer. Since the lamellae are normally pressed or punched parts or stampings, they may be brought into a shape that differs from a plane surface in the course of the same manufacturing process, for example, they may be corrugated, twisted, embossed, shaped into a profile, or perforated.

For certain purposes, shapes of lamellae may be used that cannot be derived from a plane surface, such as, for example, small rods, wire, or small tubes which may be squeezed down in the area that is inserted into the bulkhead.

A further detail in shaping the lamellae may consist in designing them in such a manner that their insertion or assembly into the bulkhead 16 is thereby facilitated; in addition, tightness or imperviousness and firmness of anchoring within bulkhead 16 may thereby be influenced.

The shape of the lamellae may also be used to influence the conditions of flow within the heat exchanger. This may, for example, be accomplished by the use of lamellae that are variously shaped according to the direction of flow. Thus, for example, as shown in FIG. 4 the fins may be shaped to increase heat exchange surface, with separating member 16a having a plurality of corrugated fins 17a extending into a first channel 30 and corrugated fins 17!) extending into a second channel 31. If desired, fins 17a may extend further into channel 30 than fins 17b extend into channel 31. Also, if desired, holes 32 may be provided in the fins in order to further increase the heat exchange surface.

Alternatively, as shown in FIG. 5, one may arrange the fins to produce turbulent flow, such as by placing fins 17c and 17d at an angle to the direction of fluid flow so that the fluid impinges upon the flat face of the fin. A further variant is shown in FIG. 6 which has continuous fins 172 and l7fto provide lamellar flow. Naturally, one may vary the fin arrangement to have lamellar flow on one side and turbulent flow on the other, or corrugated or shaped fins on the other, thus illustrating the versatility of the present invention.

Bulkhead 16 will usually be made of plastic. The polymeric materials of construction excel by virtue of their low weight, their good adaptabilty to the requirements of stability against the media that are to circulate in the heat exchanger and also due to their good workability. Thus for example, blocks as shown in FIG. 2 may be produced by casting or injection molding in a single manufacturing step. In the other embodiments according to FIG. 3, parts 18 and 19 may be prefabricated by pressing or injection molding for subsequent assembly with the lamellae. Typical plastics include polyolefins, polyvinyl chloride, polycarbonates and the like. Typical fin materials include preferably copper, aluminum and their alloys. The fins may be coated with lacquers or plastic or clad with other poorly heat conducting but corrosion resistant layers without substantially influencing the heat transfer efficiency of said fins provided that such poorly conducting coatings or layers are thin.

One can readily see the considerable advantages of the present heat exchanger. Brazing and difficult forming operations are not required, as in art heat exchangers which attach fins to walls or form them out of walls. The instant heat exchanger is versatile, capable of high heat exchange efficiency and useful in corrosive environments, all with a reasonably low cost.

This invention may be embodied in other forms or carried out in other ways without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered as in all respects illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and all changes which come within the meaning and range of equivalency are intended to be embraced therein.

What isclaimed is:

l. A heat exchanger comprising: a first channel for conveying a first heat transfer fluid; a second channel for conveying a second heat transfer fluid; a corrosion resistant solid, impervious member separating said first channel and the first fluid circulating therein from the second channel and the fluid circulating therein, said member being a poor heat conductor; a plurality of heat conductive metal fins extending through said member, with a first portion of said fins only partially extending into said first channel and a second portion of said fins only partially extending into said second channel so that the second fluid circulating in the second channel is in heat exchange relationship with the first fluid circulating in the first channel due to heat being conducted substantially only by said fins, said fins being sealed in said member so that there is no fluid leakage through said member.

2. A heat exchanger according to claim 1 wherein the first portion of said fins extending into the first channel transfers substantially more heat than the second portion of said fins extending into the second channel to compensate for dissimilar heat transfer characteristics of said fluids.

3. A heat exchanger according to claim 1 wherein said member is a corrosion resistant, organic plastic material.

4. A heat exchanger according to claim 1 wherein the first portion of said fins is a different metal than the second portion of said fins.

5. A heat exchanger according to claim 1 wherein the first portion of said fins extendsfurther into said first channel than the second portion of said fins extends into said second channel.

6. A heat exchanger according to claim 1 wherein at least a portion of said fins are shaped to increase heat transfer surface.

7. A heat exchanger according to claim 6 wherein said shaped fins are corrugated.

8. A heat exchanger according to claim 1 wherein at least a portion of said fins are arranged to cause lamellar flow of the fluid adjacent said fins.

9. A heat exchanger according to claim 1 wherein at least a portion of said fins are arranged to cause turbulent flow of the fluid adjacent said fins.

10. A heat exchanger according to claim 1 including a plurality of said members assembled together to form a complete unit, wherein the fins extending through each of said assembled members do not reach the next adjacent member. 

1. A heat exchanger comprising: a first channel for conveying a first heat transfer fluid; a second channel for conveying a second heat transfer fluid; a corrosion resistant solid, impervious member separating said first channel and the first fluid circulating therein from the second channel and the fluid circulating therein, said member being a poor heat conductor; a plurality of heat conductive metal fins extending through said member, with a first portion of said fins only partially extending into said first channel and a second portion of said fins only partially extending into said second channel so that the second fluid circulating in the second channel is in heat exchange relationship with the first fluid circulating in the first channel due to heat being conducted substantially only by said fins, said fins being sealed in said member so that there is no fluid leakage through said member.
 2. A heat exchanger according to claim 1 wherein the first portion of said fins extending into the first channel transfers substantially more heat than the second portion of said fins extending into the second channel to compensate for dissimilar heat transfer characteristics of said fluids.
 3. A heat exchanger according to claim 1 wherein said member is a corrosion resistant, organic plastic material.
 4. A heat exchanger according to claim 1 wherein the first portion of said fins is a different metal than the second portion of said fins.
 5. A heat exchanger according to claim 1 wherein the first portion of said fins extends further intO said first channel than the second portion of said fins extends into said second channel.
 6. A heat exchanger according to claim 1 wherein at least a portion of said fins are shaped to increase heat transfer surface.
 7. A heat exchanger according to claim 6 wherein said shaped fins are corrugated.
 8. A heat exchanger according to claim 1 wherein at least a portion of said fins are arranged to cause lamellar flow of the fluid adjacent said fins.
 9. A heat exchanger according to claim 1 wherein at least a portion of said fins are arranged to cause turbulent flow of the fluid adjacent said fins.
 10. A heat exchanger according to claim 1 including a plurality of said members assembled together to form a complete unit, wherein the fins extending through each of said assembled members do not reach the next adjacent member. 